In order to be able to exactly adjust the slide and the cutting tool carried by it, it is necessary to exactly measure the displacement path of the slide. The displacement path is mostly measured indirectly in known tool heads by, for example, measuring the angular path of a spindle driving the slide and concluding from this the stretch covered by the slide. Inexactnesses in the path measurement are thereby created due to unavoidable tolerances which have negative effects on the exact position of the cutting tool and the reproducability of the adjustment.
In order to avoid this disadvantage, it is already known, for a tool head of the above-disclosed type (DE-OS 35 26 712), to measure the displacement path of the slide relative to the housing directly through an optical scanning of an incremental glass measuring rod fixedly connected to the slide by a sensing head arranged in the main body. The measuring light for the optical scanning of the measuring scale is thereby guided through a photoconductor from outside into the inside of the tool head. The light signals from the glass measuring rod on the scanning element are also introduced into a further measuring light conductor connected to an evaluating electronics device arranged outside of the rotating main body for evaluating the results of the path measurement. Because of the relatively complicated optoelectronic connecting technique, handling of the known tool head is complicated and cannot easily be automated. In addition, the reading of the results of the path measurement requires a stationary installation so that the use of the known tool head is limited to certain machine tools containing this installation.
Starting out from this, the basic purpose of the invention is to provide a tool head of the abovementioned type which can be universally utilized and guarantees a breakdown-free and exact displacement path display.
The solution of the invention is, among others, based on the recognition that a universal use of the tool head is only possible when the measuring and evaluating electronics device for the direct displacement path measurement is moved inside of the main body and the particularities of the operation on high-speed machine tools are considered.
Thus, a first modification of the invention suggests that the main body has a recess for receiving a battery-operated scanning and evaluating electronics device and a radially outwardly facing digital display and that the electronics device in the recess is sealed off at its periphery by a shell completely surrounding the main body, and having a viewing window for the digital display.
The shell can thereby be designed as a metal sleeve shielding the electronics device, which shell in the area of the digital display has a window opening and is lined on its inside surface with at least one annular acrylic-glass layer. The acrylic-glass layer can be glued to the metal shell or it can be injection molded into same. Furthermore, it is advantageous for the handling of the adjusting mechanism when preferably in the area of the window opening at least one externally accessible operating switch for controlling the scanning and evaluating electronics device in the shell is provided and which is externally sealed off against liquid. With the operating switch it is possible, for example to release the functions of a zero position or effecting a changing over between different measuring systems (metric measurement or inch measurement). Such a tool head suffices completely without external devices and can therefore be used particularly easily and universally.
It is furthermore suggested according to a second modification of the invention that the main body has a recess, which is open toward the measuring scale of the slide, to receive a battery-operated scanning and evaluating electronics device, that in addition a transmitting and receiving electronics device connected to the scanning and evaluating electronics device is arranged in the same or a further recess in the main body, that the electronic circuits in the recess or in the recesses are externally sealed off by a shell completely surrounding the main body, that in an outwardly open and inwardly closed annular groove or in edge-open recesses of the shell, which recesses are distributed over the periphery, there are arranged distributed over the periphery optoelectronic transmitting and receiving elements connected to the transmitting and receiving electronics device, and that an external remote-control electronics device is provided which reacts to signals emitted by the transmitting and receiving electronics device and/or loads same with control signals. In order to guarantee in a high-speed tool head a uniform signal transmission and a uniform reception, the transmitting and receiving elements are, according to a preferred embodiment of the invention, arranged in a closed diffuser ring countersunk in the annular groove of the shell. This arrangement has, compared with the first modification, the advantage that even when the tool head rotates, a continuous reading or rather evaluating of the displacement path measured values is possible. This is particularly important when the slide is automatically adjusted, for example, through the tool spindle or through a motoric adjusting mechanism integrated into the tool head. By equipping the scanning and evaluating electronics device or the remote-control system with a microprocessor circuit and data store, it is furthermore possible with such an arrangement to relatively easily carry out a statistic process control (SPC). During the SPC, all measured data of a production process are transmitted into a processor for statistic evaluation. The measurement data can be temporarily stored and can from there be transmitted from time to time to a central processor for further evaluation.
A particularly effective seal of the recesses containing the electronic circuits is achieved when the shell is clamped between a shoulder on the main body and a flange by several axial clamping screws circumferentially spaced apart over the periphery, and extending through axial bores in the main body. Furthermore, it is important in both modifications of the invention that a hermetically sealable battery compartment is arranged in the main body.
The slide carries according to the invention a measuring scale and the main body carries a sensor scanning the measuring scale and connected to a scanning and evaluating electronics device. It is basically also possible for the main body to carry the measuring scale and the slide carry a sensor scanning the measuring scale and connected to the scanning and evaluating electronics device. It has now been proven that for an exact length measurement with capacitive and optical measuring systems, in which two scales are moved relative to one another and are scanned, the parts moved relative to one another must be every exactly associated with one another. When the parts rotate, care is taken that the acceleration and centrifugal forces acting onto the parts are compensated for in order not to obtain a speed-dependent length measurement. According to a preferred embodiment of the invention, it is therefore suggested that the measuring scale and the sensor be arranged neutral with respect to the centrifugal force in the direct vicinity of the axis of rotation of the main body. The measuring scale and the sensor are thereby advantageously arranged in planes facing one another, separated by a narrow gap from one another, and perpendicular with respect to the axis of rotation, with the axis of rotation extending through said planes. In view of the exactness in measurement, it is advantageous when the gap width is less than 20 .mu.m, preferably less than 10 .mu.m. When the measuring scale and the sensor are parts of a capacitive length-measuring device connected to the scanning and evaluating electronics device, the gap can be filled with a preferably highly viscous dielectric which does permit a movement of the two parts toward one another, however, is not urged out of the gap under the action of centrifugal force acting on the rotating tool.
The measuring structures forming the measuring scale and the sensor are advantageously arranged on a glass carrier, preferably are applied to same by means of a thin-layer technique. Due to the high form stability and the low thermal expansion coefficient of glass, mechanical and thermal influences on the path measurement result are kept low. On the other hand, care must be taken that the sensor or the measuring scale is fastened to a mounting surface of the main body or to the slide which is aligned exactly perpendicularly with respect to the axis of rotation. In order to achieve this, the flat glass carrier can, according to an advantageous embodiment of the invention, be glued with its active surface to two spaced mounting bars, while the free ends of mounting bars which project beyond an edge of the glass-carrier can be fastened, preferably clamped, to the mounting surface, which mounting surface is provided with a recess for receiving the glass carrier which faces toward the main body. In order to enable a collision-free movement of the slide, recesses to receive the mounting bars are arranged in the slide. Furthermore, a mounting surface for the glass carrier of the measuring scale or the sensor can be provided on the slide, which mounting surface is aligned perpendicularly with respect to the axis of rotation, with the glass carrier being able to be mounted onto bolts projecting from the mounting surface, being able to be pressed flat against the mounting surface and, if necessary, being able to be connected to same by means of moldable resin.
According to a further advantageous embodiment of the invention, a radially aligned battery compartment arranged in the main body to receive a flashlight battery and having a pole rod arranged near the axis and radially movable against the force of a radially inwardly, initially tensioned, spring and a metallic compartment lid preferably designed as a grounded pole screw threadedly sealed off against liquid to the main body. These precautions guarantee an essentially centrifugal-force-neutral arrangement of the flashlight battery supported on the compartment lid and the length tolerances of which are balanced compensating the centrifugal force by the spring-loaded pole rod. The pole rod can thereby be movably supported in an insulating plastic part inserted into a main body recess.
According to a further preferred embodiment of the invention, the shell surrounding the main body consists of an impact-resistant, preferably glass-fiber-reinforced plastic, in which is arranged a viewing window for the digital display. The viewing window is thereby advantageously arranged in a flat part of the otherwise cylindrical shell. Furthermore, it is possible to arrange near the viewing window, preferably in the flat part of the shell, externally operable switches to control the scanning and evaluating electronics device. The shell can be clamped advantageously between an annular shoulder on the main body and a flanged lid connectable to the main body. The viewing window is slightly radially recessed in the housing. The same is true for the switches projecting from the shell in the area of the viewing window. In order to avoid incorrect operations or damage to the viewing window and the switches, the annular shoulder and the flanged lid project at least in the flat area radially beyond the outer surface of the shell.
An adjusting mechanism for the slide is provided according to the invention for a fine adjustment and which includes a spindle supported off-center in the main body and carries a guide structure in the form of a helical tooth system and a counterpart provided with a complimentary helical tooth system and fixedly connected to the slide. The helically-toothed counterpart can, during a premounting, be first connected floatingly to the slide and can be moved into a clearance free, direction-exact orientation with the helically toothed guide structure. In this position, it is then possible to fixedly connect the helically toothed counterpart with the slide, for example, by injection molding with a moldable resin, and, if necessary, it is possible to subsequently weld the counterpart to same.
The scanning and evaluating electronics device can, according to the invention, be equipped with a digital store which, in connection with the path-measuring device and the digital display, is used, according to the invention, to determine and store the following values:
a relative value scannable on the measuring scale by means of a sensor, and defining the displacement path of the slide relative to the main body, which relative value can be set to zero in any desired displacement position of the slide, can be stored in the digital store and can be called from same into the digital display;
an absolute value scannable on the measuring scale by means of a sensor, and defining the absolute position of the slide relative to the main body, in the zero position of which absolute value the tool is balanced and which can be stored in the digital store and can be called from same into the digital display;
an absolute real measurement, which can be stored in the digital store and can be called from same into the digital display.